Silver halide photographic emulsion

ABSTRACT

A photographic silver halide emulsion comprising silver chlorobromide grains containing at least 80 mol % silver chloride or silver chloride grains is disclosed, wherein tabular grains having a thickness of less than 0.5 μm, a diameter of at least 0.5 μm and an aspect ratio of at least 2/1 account for at least 50% of the total projected area of the silver halide grains, and the tabular grains are formed in the presence of a compound of metal belonging to Group VIII of the Periodic Table. The high silver chloride content emulsion has a sensitivity as high as that of a silver iodobromide emulsion.

This is a continuation of application Ser. No. 07/662,591, filed Mar. 1,1991, abandoned.

FIELD OF THE INVENTION

The present invention relates to a silver halide photographic emulsion,and more particularly to a tabular silver chlorobromide emulsion havinga high silver chloride content or a tabular silver chloride emulsioneach having high sensitivity, and which emulsions are well adapted torapid processing.

BACKGROUND OF THE INVENTION

In photographic processing for photographic light-sensitive materials,it is desired to shorten the processing time and reduce the amount ofwaste solutions that are generated in processing.

A high-sensitivity negative type photographic light-sensitive materialgenerally employs a silver iodobromide emulsion; however, in order tosatisfy the above noted requirements, a silver chlorobromide emulsion ora silver chloride emulsion having a high solubility is useful. On theother hand, for reducing the amount of processing waste, it is desirableto increase the image density using a smaller amount of silver, and alsoit is well known in the art that tabular silver halide grains providefavorable properties with respect to sensitivity, graininess, sharpness,color sensitizing efficiency, etc.

Silver halide grains having a high silver chloride content, i.e., ashigh as 50 mol %, (hereinafter, "high silver chloride content grains")generally have a cubic structure. To form tabular grains having a highsilver chloride content, various specific means must be employed.

Methods for preparing tabular silver chlorobromide grains are knownincluding, for example, (1) simultaneously introducing an aqueoussolution of a chloride and an aqueous solution of a silver salt in adispersion medium in the presence of ammonia by a double jet method asdescribed in JP-B-64-8324 (the term "JP-B" as used herein means an"examined Japanese patent publication"), (2) reacting an aqueous silversalt solution and an aqueous solution of a chloride-containing halide inthe presence of aminoazaindene and a thioether bond-containing peptizeras described in JP-B-64-8326, (3) simultaneously introducing an aqueoussolution of a silver salt, an aqueous solution of a chloride, and anaqueous solution of a bromide to a dispersion medium while keeping themol ratio of chloride ion to bromide ion in the range of from 1.6:1 to258:1, and keeping the total concentration of halogen ions in the rangeof from 0.10 to 0.90 normal as described in JP-A-58-111936 (the term"JP-A" as used herein means an "unexamined published Japanese patentapplication"), (4) introducing silver ion into a dispersion mediumcontaining at least 0.5 molar chloride ion and a gelatin deflocculantformed from methionine of less than 30 μmol per gram as described inJP-A-62-163046, (5) contacting a chloride-containing halide and awater-soluble silver salt in a dispersion medium in the presence of acrystal habit changing amount of aminoazapyridine and the salt thereofas described in JP-A-63-281149, (6) mixing an aqueous silver saltsolution and an aqueous halide solution in the presence of thiourea or athiourea derivative or using a gold compound as described inJP-A-63-213836, (7) forming the silver halide grains in the presence ofa compound having a sulfur ion in a heterocyclic ring thereof asdescribed in JP-A-63-2043, and (8) forming the silver halide grains inthe presence of a carbonyl compound containing a sulfur ion in themolecule thereof or a sulfone compound as described in JP-A-63-41845.

However, a silver chlorobromide emulsion tends to fog and has a lowlight sensitivity as compared to a silver iodobromide emulsion. Also,the application of a silver chlorobromide emulsion is limited to colorphoto- graphic papers and light-sensitive materials for making printingplates using a relatively high intensity exposure.

For solving the above noted problems of high silver chloride contentemulsions, various techniques have been proposed.

For example, JP-A-58-95736, JP-A-58-108533, JP-A-60-222844, andJP-A-60-222845 disclose that for imparting high sensitivity to a highsilver chloride content emulsion, it is effective to form a grainstructure having a high silver bromide content layer in the silverhalide grains. The present inventors have found that although highsensitivity is obtained using these techniques, desensitization tends tooccur when pressure is applied to the emulsion. Also, tabular silverhalide grains having a uniform grain size distribution are difficult toprepare, such that the emulsion is not practically employed.Furthermore, it has also been found that by using these methods, it isdifficult to sufficiently improve the reciprocity law failure of thehigh silver chloride content emulsion.

JP-A-51-139323, JP-A-59-171947 and British Patent 2,109,576A describedthat high sensitivity is obtained and the reciprocity law failure isimproved by introducing to the silver halide emulsion a compound of ametal belonging to Group VIII of the Periodic Table.

Also, U.S. Pat. No. 4,269,927 describes that high sensitivity isobtained by incorporating cadmium, lead, zinc, or a mixture thereof in asurface latent image-type high silver chloride content emulsion having asilver chloride content of at least 80 mol %.

However, by using the above-described method, although a small increasein sensitivity and improvement in reciprocity law failure is observed,the resulting high silver chloride content emulsion does not providepractically useful performance.

Furthermore, European Patent 336426Al discloses a technique of obtaininghigh sensitivity by forming a high silver chloride content emulsion inthe presence of six-coordinate complex of rhenium, ruthenium, or osmiumhaving a cyan ligand.

However, the sensitivity attained is far inferior to that of a silveriodobromide emulsion which is generally used.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a high silver chloridecontent emulsion which is well adapted to rapid processing and having asensitivity as high as that of a silver iodobromide emulsion.

The present inventors have discovered that the above object is attainedby providing a photographic silver halide emulsion comprising silverchlorobromide grains containing at least 80 mol % silver chloride orsilver chloride grains, wherein tabular grains having a thickness ofless than 0.5 μm, a diameter of at least 0.5 μm, and an aspect ratio ofat least 2/1 account for at least 50% of the total projected area of thesilver halide grains, and said tabular grains are formed in the presenceof a compound of metal belonging to Group VIII of the Periodic Table.

DETAILED DESCRIPTION OF THE INVENTION

The invention is explained in detail below.

The compound of a metal belonging to group VIII of the Period Table foruse in the present invention includes compounds of iron, cobalt, nickel,ruthenium, rhodium, palladium, osmium, iridium, platinum, etc., andtypical examples of the compound are ferric chloride, potassiumferricyanide, cobalt chloride, cobalt nitrate, luteo salt, nickelchloride, nickel sulfate, ruthenium chloride, ruthenium hydroxide,rhodium chloride, ammonium hexachlorodinate, palladium chloride,palladium nitrate, potassium hexachloropalladate, osmium chloride,iridium chloride (IrCl₃ or IrCl₄), potassium iridate chloride, ammoniumhexachloroiridate, ammonium hexachloroplatinate, and potassiumhexachloroplatinate.

Of the metals belonging to Group VIII of the Periodic Table for use inthe present invention, iron rhenium, ruthenium, and osmium are preferredand in particular, the six-coordination complex of iron, rhenium,ruthenium, or osmium having 4 cyan ligands as described in EuropeanPatent 336426Al exhibit an excellent effect for increasing thesensitivity.

The addition amount of the compound of a metal belonging to Group VIIIof the Periodic Table is from 1×10⁻⁸ to 1×10⁻² mol, and preferably from1×10⁻⁶ to 1×10⁻³ mol per mol of silver halide contained in the emulsion.

In the present invention, by forming the tabular high silver chloridecontent grains in the presence of a compound of a metal belonging toGroup VIII of the Periodic Table, the metal of Group VIII is containedin the tabular grains.

The metal of Group VIII contained in the high silver chloride contentgrains may be uniformly distributed over the entire grain or may belocalized in the central portion of the grain, or may largely exist inthe outside portion of the grain as opposed to the central portion ofthe grain.

In the present invention, it is preferred that the metal of Group VIIIis largely present in the outside portions but not in the centralportion of the grain.

The tabular high silver chloride content grains for use in the presentinvention may be obtained by referring to the above-describedconventional methods in accordance with the intended application of theemulsion. However, a method of preparing tabular high silver chloridegrains by controlling the pH of the system for forming the grains in therange of from 4.5 to 8.5 using adenine as described in Japanese PatentApplication No. Hei-1-254439 and a method of using a bispyridinium saltas a crystal appearance controlling agent as described in JapanesePatent Application Nos. Sho-62-267476 and Hei-1-276527 are useful forproviding a narrow grain size distribution and high sensitivity.

The high silver chloride content grains of the present invention have asilver chloride content of at least 80 mol %, preferably at least 90 mol%, and more preferably at least 95 mol %.

The residue remaining silver halide content of the high silver chloridecontent grains may be composed of silver bromide. In this case, a phasemainly composed of silver bromide may be localized near the surface ofthe grains, or the silver halide grains may be core/shell type grains.

The tabular silver halide grains of the present invention have an aspectratio (diameter/thickness ratio) of at least 2/1, preferably from 2/1 to20/1, and more preferably from 3/1 to 8/1.

The diameter of a tabular grain is the diameter of a circle having thesame area as the projected area of the grain. In the present invention,the diameter of the tabular grain is at least 0.5 μm, and preferablyfrom 0.7 to 4 μm.

The thickness of a tabular grain is the distance between two mainparallel planes facing each other in the planes constituting the tabulargrain. In the present invention, the thickness of the tabular grains isless than 0.5 μm, and preferably less than 0.3 μm.

The grain size distribution of the silver halide grains of the presentinvention may be monodisperse or polydisperse, but a monodispersegenerally having a coefficient of variation of 25% or less andparticularly from 10 to 20% is preferred. The coefficient of variationis a quotient obtained by dividing a standard deviation of grain size(expressed in terms of diameter of circle equivalent to projected area)by a mean grain size).

In the preparation of the silver halide grains of the present invention,a silver halide solvent may be used. Useful silver halide solventsinclude, for example, thiocyanates as described, e.g., in U.S. Pat. Nos.2,222,264, 2,448,534, and 3,320,069; thioether compounds as described,e.g., in U.S. Pat. Nos. 3,271,157, 3,574,628, 3,704,130, 4,297,439, and4,276,347; thion compounds and thiourea compounds as described, e.g.,JP-A-53-144319, JP-A-53-82408, and JP-A-55-77737, and amine compounds asdescribed, e.g., in JP-A-54-100717. Also, ammonia can be used as thesilver halide solvent together with the above-described silver halidesto the extent that adverse effects do not result.

In the present invention, a method for increasing the addition rate,addition amount, and addition concentration of an aqueous silver saltsolution (e.g., an aqueous solution of AgNO₃) and an aqueous halidesolution (e.g., an aqueous solution of NaCl) over time is preferablyused for increasing the rate of growth of the grains in the productionof the silver halide grains.

The above methods are described, e.g., in British Patent 1,335,925, U.S.Pat. Nos. 3,672,900, 3,650,757, and 4,242,445, JP-A-55-142329,JP-A-55-158124, JP-A-58-113927, JP-A-58-113928, JP-A-58-111934, andJP-A-58-111936.

The tabular silver halide emulsion of the present invention is notnecessarily chemically sensitized but, if necessary, may be subjected tochemical sensitization.

Useful chemical sensitization methods include gold sensitization asdescribed, e.g., in U.S. Pat. Nos. 2,448,060 and 3,320,069, sulfursensitization using a sulfur-containing compound as described, e.g., inU.S. Pat. No. 2,222,264, selenium sensitization using a seleniumcompound, reduction sensitization with a tin salt, thiourea dioxide,polyamine, etc., as described, e.g., in U.S. Pat. Nos. 2,487,850,2,518,698, and 2,521,925, and a combination of these methods.

For the silver halide emulsion of the present invention, a goldsensitization method, a sulfur sensitization method, or a combinationthereof is particularly preferred.

The photographic silver halide emulsion of the present invention canfurther contain ordinary silver halide grains in addition to the silverhalide grains of the invention.

In the photographic silver halide emulsion of the present inventioncontaining tabular high silver chloride content grains, the tabular highsilver chloride content grains account for at least 50%, preferably atleast 70%, and particularly preferably at least 90% of the totalprojected area of all of the silver halide grains.

The photographic silver halide emulsion of the present invention may bemixed with other photographic silver halide emulsions and in this case,it is preferred that the tabular high silver chloride grains of thepresent invention account for at least 50% of the total projected areaof the silver halide grains in such a mixed emulsion.

The photographic silver halide emulsion of the present invention may bespectrally sensitized by a methine dye, etc. Examples of spectralsensitizing dyes for use in the present invention include cyanine dyes,merocyanine dyes, complex cyanine dyes, complex merocyanine dyes,holopolar cyanine dyes, hemicyanine dyes, styryl dyes, and hemioxonoldyes. Particularly useful dyes include cyanine dyes, merocyanine dyes,and complex cyanine dyes.

The above dyes can contain a basic heterocyclic nucleus usually utilizedfor cyanine dyes, including a pyrroline nucleus, an oxazoline nucleus, athiazoline nucleus, a pyrrole nucleus, an oxazole nucleus, a thiazolenucleus, a selenazole nucleus, an imidazole nucleus, a tetrazolenucleus, a pyridine nucleus, etc.; a nucleus formed by fusing analiphatic hydrocarbon ring to the above-noted nuclei, and a nucleusformed by fusing an aromatic hydrocarbon ring to the above-noted nuclei,such as an indolenine nucleus, a benzindolenine nucleus, an indolenucleus, a benzoxazole nucleus, a naphthoxazole nucleus, a benzothiazolenucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, abenzimidazole nucleus, a quinoline nucleus, etc., can be used for theabove-described dyes. These nuclei may be substituted on carbon atomsthereof.

Merocyanine dyes or complex merocyanine dyes for use in the presentinvention may contain a 5-membered or 6-membered heterocyclic nucleussuch as a pyrazoline-5-one nucleus, a thiohydantoin nucleus, a2-thiooxazoline-2,4-dione nucleus, a thiazoline-2,4-dione nucleus, arhodaine nucleus, a thiobarbituric acid, etc., as a nucleus having aketomethylene structure.

Examples of sensitizing dyes for use in the present invention includethe compounds described in Research Disclosure, Vol. 176 (RD 17643), IV,page 23 (December, 1978), and the literature references cited therein.

The spectral sensitizing dyes may be added to the silver halide emulsionat any step during the preparation of the emulsion. For example, thespectral sensitizing dyes may be added in the step after completingchemical sensitization but before coating, the spectral sensitizing dyescan be added simultaneously with the addition of a chemical sensitizerto simultaneously carry out spectral sensitization and chemicalsensitized as described in U.S. Pat. Nos. 3,628,969 and 4,225,666, thespectral sensitizing dyes may be added before chemical sensitization asdescribed in JP-A-58-113928, and the spectral sensitizing dyes may beadded before completion of the precipitation of the silver halide grainsto initiate the spectral sensitization.

Furthermore, the above-described spectral sensitizing dyes may beseparately added at different times during the preparation of theemulsion as described in U.S. Pat. No. 4,225,666. Namely, a portion ofthe sensitizing dye may be added prior to chemical sensitization and theremainder can be added after chemical sensitization. Thus, the spectralsensitizing dyes may be added as in the method described in U.S. Pat.No. 4,183,756, or may be added at any step of forming the silver halidegrains.

The amount of the spectral sensitizing dye added to the emulsion is from4×10⁻⁶ to 8×10⁻³ mol, and preferably from 5×10⁻⁵ to 2×10⁻³ mol per molof the silver halide.

The silver halide emulsion of the present invention can be used forcolor photographic light-sensitive materials and black-and-whitelight-sensitive materials.

The color photographic light-sensitive materials which advantageouslycontain the silver halide emulsion of the present invention includecolor photographic papers, color photographic films for photographing,color reversal films, etc., and the black-and-white light-sensitivematerials include X-ray films, general photographic films forphotographing, light-sensitive film for making printing plates, but theemulsion of the present invention is particularly preferably used forX-ray films.

There is no particular restriction on the photographic materials towhich the emulsion of the present invention is applied. Additives foruse in the silver halide emulsion of the present invention are describedin Research Disclosures, Vol. 176 (RD 17643) and Vol. 187 (RD 18716).

The above noted portions of RD 17643 and RD 18716 concerning the use ofadditives are summarized in the following table.

    ______________________________________                                        Kind of Additives                                                                             RD 17643   RD 18716                                           ______________________________________                                        1.   Chemical Sensitizer                                                                          Page 23    Page 648,                                                                     right column                                   2.   Sensitivity    --         Page 648,                                           Increasing Agent          right column                                   3.   Spectral Sensitizer                                                                          Pages 23   Page 648, right                                     and Super Color                                                                              to 24      column to page                                      Sensitizer                649, right column                              4.   Whitening Agent                                                                              Page 24    --                                             5.   Antifoggant and                                                                              Pages 24   Page 649,                                           Stabilizer     to 25      right column                                   6.   Light-Absorber,                                                                              Pages 25   Page 649, right                                     Filter Dye and Ultra-                                                                        to 26      column to page                                      violet Absorber           650, left column                               7.   Stain Inhibitor                                                                              Page 25,   Page 650, left                                                     right      to right                                                           column     column                                         8.   Dye Image Stabilizer                                                                         Page 25    --                                             9.   Hardener       Page 26    Page 651,                                                                     left column                                    10.  Binder         Page 26    Page 651,                                                                     left column                                    11.  Plasticizer    Page 27    Page 650,                                           Lubricant                 right column                                   12.  Coating Aid    Pages 26   Page 650,                                           Surface Active Agent                                                                         to 27      right column                                   13.  Antistatic Agent                                                                             Page 27    Page 650,                                                                     right column                                   ______________________________________                                    

Of the above-described additives, as anti-foggants and stabilizers,azoles (e.g., benzothiazolium salts, nitroimidazoles,nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles,nitroindazoles, aminotriazoles, and benzotriazoles); heterocyclicmercapto compounds (e.g., mercaptothiazoles, mercaptobenzothiazoles,mercaptobezimidazoles, mercaptothiadiazoles, mercaptotetrazoles(particularly, 1-phenyl-5-mercaptotetrazole); mercaptopyrimidine, andmercaptotriazine); the above-noted heterocyclic mercapto compoundshaving a water-solubilizing group such as a carboxy group and a sulfongroup; thioketo compounds such as oxazolinethione, etc.;azaindenes[e.g., triazaindenes, tetraazaindenes (particularly,4-hydroxy-substituted 1,3,3a,7-tetraazaindenes), and pentaazaindenes];benzenethiosulfonic acids; benzenesulfinic acids; benzenesulfonamide,etc., are preferably used.

Color couplers for use in the present invention, include non-diffusiblecouplers having a hydrophobic group (i.e., a "ballast group") in themolecule thereof, or polymerized couplers are preferred. The coupler maybe four-equivalent or two equivalent to silver ion. Furthermore, thesilver halide emulsion of the present invention may further contain acolored coupler having a color correction effect or a DIR coupler whichreleases a development inhibitor upon development. Also, the emulsionmay contain a colorless DIR coupling compound which forms a colorlessproduct by a coupling reaction and releases a development inhibitor.

Examples of the magenta coupler for use in the present invention include5-pyrazolone couplers, pyrazolobenzimidazole couplers, pyrazolotriazolecouplers, pyrazolotetrazole couplers, cyanoacetylcoumarone couplers, andopen-chain acylacetonitrile couplers. Examples of the yellow couplersare acylacetamide couplers (e.g., benzylacetanilides andpivaloylacetanilides). Also, examples of the cyan couplers are naphtholcouplers and phenol couplers. As the cyan coupler, phenolic couplershaving an ethyl group at the meta-position of the phenol,2,5-diacylamino-substituted phenolic couplers, phenolic couplers havinga phenylureido group at the 2-position and an acylamino group at the5-position, and couplers having a sulfonamido group or an amido group atthe 5-position of the naphthol as described in U.S. Pat. Nos. 3,772,002,2,772,162, 3,758,308, 4,126,396, 4,334,011, 4,327,173, 3,446,622,4,333,999, 4,451,559, and 4,427,767 are preferred in that the imagesthereby formed have an excellent fastness.

Two or more kinds of the above noted couplers may be incorporated in thesame emulsion layer, or the same coupler may be incorporated into two ormore different layers to satisfy the characteristics required for thephotographic light-sensitive material.

The silver halide emulsion of the present invention may further containa fading inhibitor and typical examples of the fading inhibitor arehydroquinones, 6-hydroxychromans, 5-hydroxycoumarans, spirochromans,p-alkoxyphenols, hindered phenols such as bis-phenols, etc., gallic acidderivatives, methylenedioxybenzenes, aminophenols, hindered amines, andether or ester derivatives formed by silylating or alkylating thephenolic hydroxy group of each of these compounds. Also, metal complexessuch as bis(salicylaldoxymate) nickel complex andbis(N,N-dialkyldithiocarbamate) nickel complex can be used.

For processing the photographic light-sensitive material containing thesilver halide emulsion of the present invention, known processes can beused and also known processing solutions can be used for this purpose.

The processing temperature is usually selected from the range of from18° C. to 50° C., but the processing temperature may be lower than 18°C. or higher than 50° C. According to the intended application, ablack-and-white process for forming silver images or a color developmentprocess including a development for forming color images can be used.

For black-and-white development, known developing agents such asdihydroxybenzenes (e.g., hydroquinone), 3-pyrazolidones (e.g.,1-phenyl-3-pyrazolidone), aminophenols (e.g., N-methyl-p-aminophenol)can be used alone or in combination thereof.

The color developer is generally composed of an alkaline aqueoussolution containing a color developing agent. As the color developingagent, known primary aromatic amine color developing agents such asphenylenediamines [e.g., 4-amino-N,N-diethylaniline,3-methyl-4-amino-N,N-diethylaniline,4-amino-N-ethyl-N-(β-hydroxyethyl)aniline,3-methyl-4-amino-N-ethyl-N-(β-methanesulfonamidoethyl ")aniline, and4-amino-3-methyl-N-ethyl-N-(-β-methoxyethyl)aniline]can be used.

Other color developing agents for use in the present invention aredescribed in L. F. A. Mason, Photoqraphic Processinq Chemistry, pages226 to 229, (published by The Focal Press, 1966), U.S. Pat. Nos.2,193,015 and 2,592,364, and JP-A-48-64933.

The developer may further contain a pH buffers such as sulfites,carbonates, borates, and phosphates of alkali metals and a developmentinhibitor or antifoggants such as bromides, iodides, and organicantifoggants.

Also, if necessary, the developer may further contain a water softener,a preservative such as hydroxylamine, etc., an organic solvent such asbenzyl alcohol, diethylene glycol, etc., a development accelerator suchas polyethylene glycol, quaternary ammonium salts, amines, etc., adye-forming coupler, a competing coupler, a fogging agent such as sodiumboron hydride, etc., an auxiliary developing agent such as1-phenyl-3-pyrazolidone, etc., a tackifier, the polycarboxylic acidseries chelating agent described in U.S. Pat. No. 4,083,723, and theantioxidant described in West German Patent Application (OLS) 2,622,950.

Furthermore, in the development processing of the photographic materialcontaining the silver halide emulsion of the present invention, thedeveloper may further contain a silver staining inhibitor such as thecompounds described in JP-A-56-24347.

The developer for use in accordance with the present invention cancontain an amino compound such as the alkanolamine described inJP-A-56-106244.

Additionally the compounds described in L. F. A. Mason, PhotoqraphicProcessing Chemistry, pages 226-229, (published by The Focal Press,(1966)), U.S. Pat. Nos. 2,193,015 and 2,592,364, and JP-A-48-64933 canbe also used in the developer.

A fix solution for processing a photographic material containing thesilver halide emulsion of the present invention is an aqueous solutioncontaining a thiosulfate having a pH of at least 3.8, preferably from4.2 to 7.0, and more preferably from 4.5 to 5.5.

Useful fixing agents include sodium thiosulfate and ammoniumthiosulfate, but ammonium thiosulfate is particularly preferred in viewof its rapid fixing rate. The amount of the fixing agent variesdepending on the intended application, but is generally from about 0.1mol/liter to about 6 mol/liter.

The fix solution may contain a water-soluble aluminum salt as ahardening agent, and examples of the aluminum compound are aluminumchloride, aluminum sulfate, and potassium alum.

Also, the fix solution can further contain tartaric acid, citric acid,gluconic acid and the derivatives thereof alone or as a mixture thereof.The addition amount of these additives is effectively at least 0.005mol, and particularly from 0.01 mol/liter to 0.03 mol/liter per liter ofthe fix solution.

The fix solution can, if desired, contain a preservative (e.g., sulfitesand hydrogensulfites), a pH buffer (e.g., acetic acid and boric acid), apH controlling agent (e.g., sulfuric acid), a chelating agent having awater softening ability, and the compound described in JP-A-62-78551.

For rapid processing, it is advantageous to reduce the swellingpercentage (preferably from 150% to 50%) of the photographiclight-sensitive material and to reduce the hardening action byprocessing. For the measurement of swelling percentage, a reference maybe made to U.S. Pat. No. 4,414,304. Thus, hardening is preferably notconducted during development or fixing. The hardening reaction in fixingis diminished by increasing the pH of the fix solution above 4.6.

In the processing of the silver halide photo-graphic material containingthe emulsion of the present invention, after the development and fixstep, the photographic material can be processed with wash water or astabilization solution having a replenishment rate of less than 3 liters(including 0, i.e., water washing with stored water) per square meter ofthe photographic material processed.

In other words, in the processing of a photographic material containingthe emulsion of the present invention, water-saving processing ispractically conducted and also plumbing for an automatic processor isnot necessarily required.

As a method of reducing the amount of the water washing replenisher, amultistage (e.g., 2 or 3 stage) countercurrent system may be used. Whenthe multistage countercurrent system is applied for processing aphotographic light-sensitive materials containing the silver halideemulsion of the present invention, the light-sensitive material issuccessively processed with a cleaner processing solution (without beingstained by the residual fix solution), such that washing is carried outmore efficiently.

For the above-described water-saving processing or non-plumbingprocessing, it is preferred to apply an antifungal treatment to the washwater or the stabilization solution.

Useful antifungal treatments include a method of irradiating ultravioletrays as described in JP-A-60-26393, a method of using a magnetic fieldas described in JP-A-60-263940, a method of forming pure water usingion-exchange resins as described in JP-A-61-131632, and a method ofusing antibacterial agents as described in JP-A-62-115439,JP-A-62-153952, JP A-62-220951, and A-2-209532.

Furthermore, the antibacterial agents, antifungal agents, surface activeagents, etc., described in L. E. West, "Water Quality Criteria", Photo.Sci. & Eng., Vol. 9, No. 6, (1965), M. W. Beach, "Microbiological Growthin Motion-Picture Processing", SMPTE Journal, Vol. 85, (1976), R. O.Deegan, "Photo Processing Wash Water Biocides", J. Imaging Tech. 10, No.6 (1984), and JP-A-57-8542, JP-A-57-58143, JP-A-58-105145,JP-A-57-132146, JP-A-58-18631, JP-A-57-97530, JP-A-57-157244, etc., canalso be used.

Moreover, the wash bath or the stabilization bath can contain theisothiazoline series compounds described in Kriman, J. Image Tech 10,(6), 242(1984), the isothiazoline series compounds described in ResearchDisclosure, Vol. 205, RD 20526 (May, 1981), the isothiazoline compoundsdescribed in ibid., Vol. 228, RD 22845 (April, 1983), and the compoundsdescribed in JP-A-62-209532 as microbiocides.

When wash step is carried out using a small amount of wash water, it ispreferred to use a wash bath having a squeeze roller as described inJP-A-62-32460. Also, the wash step constitution described inJP-A-63-143548 is preferably used.

When the silver halide light-sensitive material containing the silverhalide emulsion of the present invention is processed by an automaticprocessor including the steps of at least development, fix, and wash (orstabilization), the steps from development to drying are preferablycompleted within 50 seconds. Namely, the time from immersion of the topend of the light-sensitive material in the developer to the time thatthe top end emerges from a drying zone after being fixed, washed (orstabilized) and dried (i.e., the dry-to-dry time), is not more than 50seconds. It is more preferred that the dry-to-dry time is not more than30 seconds.

The reason that rapid processing having a dry-to-dry time of not morethan 50 seconds can be attained is that the development process can becarried out within 15 seconds. The development temperature is preferablyfrom 25° C. to 50° C., and more preferably from 30° C. to 40° C.

Also, the fixing temperature and time are preferably from about 20° C.to about 50° C. and 5 seconds to 20 seconds, and more preferably from30° C. to 40° C. and from 5 seconds to 10 seconds.

Furthermore, the wash or stabilization temperature and time arepreferably from 0° C. to 50° C. and from 5 seconds to 20 seconds, andmore preferably from 15° C. to 40° C. and from 5 seconds to 15 seconds.

In accordance with the present invention, the processing fluidsremaining wash water in or on the photographic light-sensitive materialafter being developed, fixed and washed (or stabilizer) is preferablyremoved by drying through a squeeze roller. Drying is carried out at atemperature of from about 40° C. to about 100° C. and the drying timecan be properly adjusted according to the surrounding ambient conditionsand is usually from about 5 seconds to 20 seconds, and more preferablyfrom about 5 seconds to 10 seconds at a temperature of from 40° C. to80° C.

When the photographic light-sensitive material containing the silverhalide emulsion of the present invention is processed in a dry-to-drytime of not more than 50 seconds, and to prevent the formation of unevendevelopment which tends to occur in rapid processing, a rubber roller ispreferably applied to the roller at the outlet of the development tankas described in JP-A-63-151943, or the jet speed for stirring thedeveloper in the developing tank is increased to at least 10 meters/min.as described in JP-A-63-151944.

Furthermore, for increasing the fixing speed or for increasing thedissolving speed of dyes contained in the light-sensitive material, theroller construction of the fixing tank preferably employs a counterroller. By employing a counter roller, the number of rollers is reducedand the processing tank size can be reduced. That is, a compactautomatic processor can be employed for processing a light-sensitivematerial containing the silver halide emulsion of the present invention.

The invention is further described in detail by reference to thefollowing examples, but the invention is not to be construed as beinglimited to these examples.

EXAMPLE 1 Preparation of Comparison Cubic Grain Silver ChlorobromideEmulsion 1

To an aqueous solution of 3% limed gelatin was added 3.3 g of sodiumchloride followed by addition of 3.2 ml of an aqueous solution of 1%N,N'-dimethylimidazolidine-2-thione. To the solution were added anaqueous solution containing 34 g of silver nitrate and an aqueoussolution containing 0.476 g of potassium bromide and 11.47 g of sodiumchloride (1st addition) at 63° C. with vigorous stirring. Then, anaqueous solution containing 136 g of silver nitrate and an aqueoussolution containing 1.904 g of potassium bromide and 45.86 g of sodiumchloride (2nd addition) were added thereto with vigorous stirring at 63°C. After keeping the mixture at 63° C. for 5 minutes, the temperaturewas lowered and the mixture was desalted and washed with water.Furthermore, 90.0 g of limed gelatin was added to the emulsion thusobtained, and pH and pAg thereof were adjusted to 7.1 and 7.5,respectively. The silver halide emulsion thus obtained contained cubicsilver halide grains having a side length of 0.8 μm.

Preparation of Comparison Cubic Grain Silver Chlorobromide Emulsion 2

The same procedure as for preparing comparison emulsion-1 was employedexcept that iron was added to the aqueous alkali halide solutions beingadded in the 1st and 2nd additions in the form of an aqueous solution ofK₄ [Fe(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silver in thesystem, to prepare the comparison emulsion 2.

Preparation of Comparison Cubic Grain Silver Chlorobromide Emulsion 3

The same procedure as for preparing comparison emulsion-1 was employedexcept that ruthenium was added to the aqueous alkali halide solutionsbeing added in the 1st and 2nd additions in the form of an aqueoussolution of K₄ [Ru(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silverin the system, to prepare the comparison emulsion 3.

Preparation of Comparison Cubic Grain Silver Chloride Emulsion 4

To an aqueous solution of 3% limed gelatin was added 3.3 g of sodiumchloride followed by addition of 3.2 ml of an aqueous solution of 1%N,N'-dimethylimidazolidine-2-thione. To the solution were added anaqueous solution containing 34 g of silver nitrate and an aqueoussolution containing 11.7 g of sodium chloride (1st addition) withvigorous stirring at 63° C. Then, an aqueous solution containing 136 gof silver nitrate and an aqueous solution containing 46.8 g of sodiumchloride were added thereto (2nd addition) with vigorous stirring at 63°C. After keeping the emulsion thus obtained at 63° C. for 5 minutes, thetemperature was lowered, and the emulsion was desalted and washed withwater. Furthermore, 90.0 g of limed gelatin and 3 g of phenoxy ethanolwere added, and the pH and pAg thereof were adjusted to 7.1 and 7.5,respectively.

The silver halide emulsion thus obtained contained cubic silver halidegrains having an edge length of 0.78 μm.

Preparation of Comparison Cubic Grain Silver Chloride Emulsion 5

The same procedure as for preparing comparison example 4 was employed,except that iron was added to the aqueous alkali halide solutions beingadded in the 1st and 2nd additions in the form of an aqueous solution ofK₄ [Fe(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silver in thesystem, to prepare the comparison emulsion 5.

Preparation of Comparison Cubic Grain Silver Chloride Emulsion 6

The same procedure as for preparing comparison emulsion 4 was employed,except that ruthenium was added to the aqueous alkali halide solutionsbeing added in the 1st and 2nd additions in the form of an aqueoussolution of K₄ [Ru(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silverin the system, to prepare the comparison emulsion 6.

Preparation of Comparison Tabular Grain Silver Chlorobromide Emulsion 7

By referring to the method described in Example 1 of JP-A-63-281149, atabular grain silver chlorobromide emulsion containing 1.5 mol % silverbromide was formed. In this case, 0.08 g of4-aminopyrazolo[3,4,d]-pyrimidine was added as a crystal growthmodifier, and the pH value was adjusted to 4.5.

After forming the silver halide grains, the temperature was lowered andthe emulsion thus formed was desalted and washed with water.Furthermore, after adding gelatin, the pH and pAg thereof were adjustedto 7.1 to 7.5, respectively. The weight ratio of gelatin to silvernitrate was adjusted to the same value (by weight) as that of comparisonemulsions 1 to 6.

The tabular silver halide grains thus obtained had a thickness of 0.19μm, a diameter of 1.45 μm, and an aspect ratio of 7.6.

Preparation of Tabular Grain Silver Chlorobromide Emulsion 8 of theInvention

The same procedure as for preparing Comparison Example 7 was employed,except that iron was added in the form of an aqueous solution of K₄[Fe(CN)₆ ] to the aqueous alkali halide solutions in an amount of 1×10⁻⁴mol per mol of silver in the system, to prepare the emulsion 8 of theinvention.

Preparation of Tabular Grain Silver Chlorobromide Emulsion 9 of theInvention

The same procedure as for preparing Comparison Example 7 was employed,except that ruthenium was added to the aqueous alkali halide solutionsin the form of an aqueous solution of K₄ [Ru(CN)₆ ] in an amount of1×10⁻⁴ mol per mol of silver in the system, to prepare the emulsion 9 ofthe present invention.

Preparation of Comparison Tabular Grain Silver Chloride Emulsion 10

The silver chloride emulsion was prepared as follows.

    ______________________________________                                        Solution (1):                                                                 Inactive Gelatin        30     g                                              Adenine Sulfate         0.186  g                                              [(C.sub.5 H.sub.5 N.sub.5).sub.2.H.sub.2 SO.sub.4.2H.sub.2 O]                 NaCl                    7.8    g                                              Water                   1450   ml                                             Solution (2):                                                                 AgNO.sub.3              20     g                                              Water to make           50     ml                                             Solution (3):                                                                 NaCl                    6.5    g                                              Water to make           50     ml                                             Solution (4):                                                                 AgNO.sub.3              150    g                                              Water to make           400    ml                                             Solution (5):                                                                 NaCl                    52     g                                              Water to make           400    ml                                             ______________________________________                                    

The pH value of the solution (1) containing adenine sulfate and NaClmaintained at 75° C. was adjusted to 7.0 and while vigorously stirringthe solution, the solution (2) and the solution (3) were simultaneouslyadded to the solution over a period of 5 minutes at constant additionrates. Then, the solution (4) and the solution (5) were simultaneouslyadded thereto at constant addition rates over a period of 40 minutes toprovide a silver chloride emulsion.

After desalting by flocculation and washing with water, 90 g of gelatinand 3 g of phenoxy ethanol were added to the emulsion, and pH and pAgthereof were adjusted to 7.1 and 7.5, respectively

The tabular silver halide grains thus prepared had a diameter of 1.4 μm,a thickness of 0.20 μm, and an aspect ratio of 7.0.

Preparation of Tabular Grain Silver Chloride Emulsion 11 of theInvention

The same procedure as for preparing the emulsion 10 was employed, exceptthat iron was added to the solution (5) in the form of an aqueoussolution of K₄ [Fe(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silverin the system, to prepare the emulsion 11 of the invention.

Preparation of Tabular Grain Silver Chloride Emulsion 12 of theInvention

The same procedure as for preparing the emulsion 10 was employed, exceptthat ruthenium was added to the solution (5) in the form of an aqueoussolution of K₄ [Ru(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silverin the system, to prepare the emulsion 12 of the invention.

Preparation of Emulsion Coating Composition

To each of the emulsions 1 to 12 were added the following components permol of silver halide to provide corresponding coating compositions.

    ______________________________________                                        Polymer Latex: [poly(ethyl acrylate/                                                                    20.0   g                                            methacrylic acid) = 97/3]                                                     Hardening Agent: 1,2-Bis(vinylsulfonyl-                                                                 2.4    g                                            acetamido)ethane                                                              2,6-Bis(hydroxyamino)-4-  76     mg                                           diethylamino-1,3,5-triazine                                                   Sodium Polyacrylate (mean molecular                                                                     2.1    g                                            weight 41,000)                                                                Potassium Polystyrenesulfonate                                                                          1.0    g                                            (mean molecular weight 600,000)                                               Dextran (molecular weight 39,000)                                                                       23.6   g                                            Trimethylolpropane        9.8    g                                             ##STR1##                 0.03   g                                            ______________________________________                                    

Preparation of Support

A base was prepared by forming a subbing layer having a coated amount ofgelatin of 84 mg/m² on a polyethylene terephthalate base of 175 μm inthickness.

Preparation of Photographic Material

Each of the above-described coating compositions were simultaneouslycoated on the above-noted support together with the following coatingcomposition for a surface protective layer. The silver halide coveragewas 2.0 g/m² (in terms of silver).

The coating composition for the surface protective layer is as shownbelow. Thus, photographic light-sensitive materials 1 to 12 as shown inTable 1 were prepared.

    ______________________________________                                        Content of Surface Protective Layer                                                                   Coated Amount                                         ______________________________________                                        Gelatin                 1.138 g/m.sup.2                                       Dextran (mean molecular weight                                                                        0.228 g/m.sup.2                                       39,000)                                                                       4-Hydroxy-6-methyl-1,3,3a,7-                                                                          0.0155 g/m.sup.2                                      tetraazaindene                                                                Sodium Polyacrylate (mean                                                                             0.023 g/m.sup.2                                       molecular weight 400,000)                                                      ##STR2##               0.0225 g/m.sup.2                                      C.sub.16 H.sub.33 O(CH.sub.2 CH.sub.2 O) .sub.10 H                                                    0.035 g/m.sup.2                                        ##STR3##               0.005 g/m.sup.2                                       C.sub.8 F.sub.17 SO.sub.3 K                                                                           0.0053 g/m.sup.2                                      Polymethyl Methacrylate 0.088 g/m.sup.2                                       (mean grain size 3.7 μm)                                                   Proxicel (available from I.C.I. Co)                                                                   0.0006 g/m.sup.2                                      ______________________________________                                    

Exaluation of Photographic Performance

Each of the photographic materials 1 to 12 thus prepared was imagewiseexposed for 1/50 sec. using a light source of 365.5 nm in wavelength andprocessed using following developer (I) and fix solution (I), and thendried.

    ______________________________________                                        Developer (I)                                                                 Hydroquinone            10     g                                              4-Hydromethyl-4-methyl-1-                                                                             1      g                                              phenyl-3-pyrazolidone                                                         Potassium Chloride      10     g                                              Ascorbic Acid           10     g                                              pH adjusted to          9.5                                                   Water to make           1      liter                                          Fix Solution (I)                                                              Ammonium Thiosulfate    200    g                                              Sodium Sulfite (anhydrous)                                                                            20     g                                              Boric Acid              8      g                                              Ethylenediaminetetraacetic Acid                                                                       0.1    g                                              Di-Sodium                                                                     Aluminum Sulfate        15     g                                              Sulfuric Acid           2      g                                              Glacial Acetic Acid     22     g                                              Water to make           1.0    liter                                          pH adjusted to          4.2                                                   ______________________________________                                    

The development was carried out for 15 seconds at 30° C. and the fix wascarried out for 10 seconds at 30° C.

The sensitivity was evaluated as the reciprocal of the exposure amountnecessary for obtaining blackened extent of 0.3+fog value, relative tothe sensitivity of photographic material 1 defined as 100.

The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                                 Amount of                                        Photographic                                                                           Halogen Grain                                                                              Metal  Metal Salt                                                                            Sensi-                                   Material Composition                                                                           Form Salt Used                                                                            (mol/mol-Ag)                                                                          tivity                                   __________________________________________________________________________              Cl 98 mol %                                                         1                Cubic                                                                              None   0       100                                               Br  2 mol %                                                                    Cl 98 mol %                                                         2                "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   105                                               Br  2 mol %                                                                    Cl 98 mol %                                                         3                "    K.sub.4 [Ru(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   105                                               Br  2 mol %                                                          4        Cl 100 mol %                                                                          "    None   0       100                                      5        "       "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   115                                      6        "       "    K.sub.4 [Ru(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   110                                                Cl 98.5 mol %                                                       7                Tabular                                                                            None   0        90                                               Br  1.5 mol %                                                                  Cl 98.5 mol %                                                        8*              Tabular                                                                            K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   120                                               Br  1.5 mol %                                                                  Cl 98.5 mol %                                                        9*              Tabular                                                                            K.sub.4 [Ru(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   120                                               Br  1.5 mol %                                                        10       Cl 100 mol %                                                                          "    None   0        90                                      11*      "       "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   135                                      12*      "       "    K.sub.4 [Ru(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   130                                      __________________________________________________________________________     *Invention                                                               

From the results shown in Table 1, it is seen that in the comparison ofemulsions 1, 4, 7, and 10 containing no metal salt, cubic silver halidegrains have a higher sensitivity than tabular silver halide grains. Thisresult is obtained because the light absorption of tabular silver halidegrains is less than that of cubic silver halide grains. However, whenthe silver halide grains are formed in the presence of iron orruthenium, the tabular silver halide grains exhibit remarkedly highersensitivity than the cubic silver halide grains despite less lightabsorption. The above results clearly show the effect of the presentinvention.

EXAMPLE 2 Preparation of Comparison Cubic Grain Emulsion 13

A silver halide emulsion was prepared in the same manner as emulsion 4of Example 1. However, in this case, after completing the 1st and 2ndadditions of the alkali halide, an aqueous solution containing 1.19 g ofpotassium bromide was added to carry out halogen conversion at thesurface of the silver halide grains. Thereafter, the emulsion was dealtand washed. Then, 90 g of gelatin and 3 g of phenoxy ethanol were added,and the pH and pAg were adjusted to 6.5 and 7.5, respectively, to obtainthe emulsion 13.

Preparation of Comparison Cubic Grain Emulsion 14

The same procedure as for preparing emulsion 13 was employed, exceptthat iron was added to the aqueous alkali halide solutions being addedin the 1st and 2nd additions in the form of an aqueous solution of K₄[Fe(CN)₆ ] in an amount of 1×10⁻⁴ mol per mol of silver in the system,to prepare the emulsion 14.

Preparation of Comparison Tabular Emulsion 15

A silver halide emulsion was prepared in the same manner as emulsion 10in Example 1. However, in this case, after completing the addition ofthe solutions (4) and (5) an aqueous solution containing 1.19 g ofpotassium bromide was added to the emulsion to carry out halogenconversion of the surface of the silver halide grains.

Then, after desalting and washing with water, 90 g of gelatin and 3 g ofphenoxy ethanol were added to the emulsion, and the pH and pAg thereofwere adjusted to 6.5 and 7.5, respectively, to obtain the emulsion 15.

Preparation of Tabular Grain Emulsion 16 of the Invention

A silver halide emulsion was prepared in the same manner as emulsion 11in Example 1.

In this case, however, after completing the addition of the solutions(4) and (5), an aqueous solution containing 1.19 g of potassium bromidewas added to the emulsion to carry out halogen conversion of the surfaceof the silver halide grains.

Preparation of Photographic Materials and Evaluation

By following the same procedure as Example 1, photographic materials 13to 16 were prepared and were evaluated as in Example 1.

The results obtained are shown in Table 2 below.

                                      TABLE 2                                     __________________________________________________________________________                                    Amount of                                     Photographic                                                                           Halogen    Grain                                                                              Metal  Metal Salt                                                                            Sensi-                                Material Composition                                                                              Form Salt Used                                                                            (mol/mol-Ag)                                                                          tivity                                __________________________________________________________________________     4       Cl 100 mol %                                                                             Cubic                                                                              None   0       100                                             Cl 99 mol %                                                         13                  "    None   0       145                                            Br 1 mol %                                                                    (Halogen conversion)                                                           Cl 99 mol %                                                         14                  "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   160                                            Br 1 mol %                                                                    (Halogen conversion)                                                 10       Cl 100 mol %                                                                             Tabular                                                                            None   0        90                                             Cl 99 mol %                                                         15                  "    None   0       130                                            Br 1 mol %                                                                    (Halogen conversion)                                                           Cl 99 mol %                                                          16*                "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 ×  10.sup.-4                                                                  195                                            Br 1 mol %                                                                    (Halogen conversion)                                                 __________________________________________________________________________     *Invention                                                               

From the results shown in Table 2, it can be seen that the effects ofthe present invention are further enhanced by using silver halide grainssubjected to halogen conversion.

EXAMPLE 3 Preparation of Comparison Cubic Grain Emulsion 17

The same procedure as for preparing emulsion 5 was employed to prepare asilver halide emulsion which was not chemically sensitized. In thiscase, however, the pH and pAg were adjusted to 7.1 and 6.95,respectively.

To the emulsion, the following components were successively added tochemically sensitize the emulsion at 60° C.

    ______________________________________                                                        (per mol of silver)                                           ______________________________________                                        NaCl              1.79 × 10.sup.-2 mol                                  KBr               1 × 10.sup.-2 mol                                     Chloroauric Acid  5 × 10.sup.-5 mol                                     Sodium Thiosulfate                                                                              5 × 10.sup.-5 mol                                     4-Hydroxy-6-methyl-1,3,3a,7-                                                                    5 × 10.sup.-3 mol                                     tetraazaindene                                                                ______________________________________                                    

Chemical ripening was carried out for 30 minutes after adding 4hydroxy-6-methyl-1,3,3a,7-tetraazaindene.

Preparation of Tabular Grain Emulsion 18 of the Invention

The same procedure as for preparing the emulsion 11 of invention wasemployed to prepare emulsion which was not chemically sensitized. Inthis case, however, the pH and pAg thereof were adjusted to 7.1 and6.95, respectively. The silver halide was then chemically sensitized inthe same manner as emulsion 17 to obtain the emulsion 18 of theinvention.

Preparation of Comparison Tabular Grain Emulsion 19

A silver chlorobromide emulsion was prepared as follows.

    __________________________________________________________________________    Solution (1):                                                                 Inactive Gelatin                    30 g                                       ##STR4##                           0.8                                                                              g                                      NaCl                                4  g                                      Water to make                       1750                                                                             ml                                     Solution (2):                                                                 AgNO.sub.3                          34 g                                      Water to make                       200                                                                              ml                                     Solution (3):                                                                 NaCl                                12.5                                                                             g                                      Water to make                       200                                                                              ml                                     Solution (4):                                                                 AgNO.sub.3                          102                                                                              g                                      Water to make                       600                                                                              ml                                     Solution (5):                                                                 NaCl                                37.5                                                                             g                                      Water to make                       600                                                                              ml                                     __________________________________________________________________________

To the solution (1) kept at 35° C. with vigorous stirring weresimultaneously added the solution (2) and the solution (3) over a periodof 10 minutes.

Furthermore, after raising the temperature of the mixture to 75° C., thesolution (4) and the solution (5) were simultaneously added thereto overa period of 30 minutes.

The emulsion was desalted by an ordinary flocculation method and washedwith water, and after adding thereto gelatin, the pH and pAg wereadjusted to 6.4 and 7.5 at 40° C. to provide a tabular grain silverchloride emulsion.

The silver chloride emulsion thus prepared contained more than 80%(projected area) tabular grains having a thickness of less than 0.5 μm,a diameter of at least 0.5 μm, and aspect ratio of 2 or more and havingparallel (111) planes. The tabular silver halide grains had a meanprojected area of 1.8 μm², a mean thickness of 0.22 μm, and a meanaspect ratio of 6.9.

To the tabular silver chloride emulsion was added a superfine grainsilver bromide emulsion (grain size of about 0.05 μm) in an amount toprovide 1 mol % silver bromide to silver chloride, and ripening wascarried out for 10 minutes at 60° C. to provide an emulsion beforechemical sensitization.

After adjusting, the pH and pAg of the emulsion to 7.1 and 7.8,respectively, the following components were successively added tochemically sensitize the emulsion at 60° C.

    ______________________________________                                                        (per mol of silver)                                           ______________________________________                                        NaCl              1.79 × 10.sup.-2 mol                                  Chloroauric Acid  5 × 10.sup.-2 mol                                     Sodium Thiosulfate                                                                              2 × 10.sup.-5 mol                                     4-Hydroxy-6-methyl-1,3,3a,7-                                                                    5 × 10.sup.-3 mol                                     tetraazaindene                                                                ______________________________________                                    

The chemical ripening time was 30 minutes.

Preparation of Tabular Grain Emulsion 20 of the Invention

The same procedure as for preparing the emulsion 19 was employed, exceptthat iron was added to the solution (5) in the form of an aqueoussolution of K₄ [Fe(CN)₆ ] in an amount of 1×10⁻⁴ per mol of silver inthe system. Then, the emulsion was chemically sensitized in the samemanner as emulsion 19.

Preparation of Photographic Materials and Evaluation

Photographic materials 17 to 20 were prepared and evaluated in the samemanner as in Example 1. The development process was carried out for 10seconds at 35° C.

The results are shown in Table 3 below, wherein the sensitivity isindicated relative to the photographic material 4 defined as 100.

                                      TABLE 3                                     __________________________________________________________________________                                 Amount of                                        Photographic                                                                           Halogen Grain                                                                              Metal  Metal Salt                                                                            Chemical                                                                              Sensi-                           Material Composition                                                                           Form Salt Used                                                                            (mol/mol-Ag)                                                                          Sensitization                                                                         tivity                           __________________________________________________________________________     4       Cl 100 mol %                                                                          Cubic                                                                              None   0       None     100                             17        Cl 99 mol %                                                                          "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   Gold     8500                                                                 sensitization +                                   Br 1                        sulfur                                                                        sensitization                             18*      Cl 99 mol %                                                                          Tabular                                                                            K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   Gold    11200                                                                 sensitization +                                   Br 1                        sulfur                                                                        sensitization                            19        Cl 99 mol %                                                                          "    None   0       Gold     7950                                                                 sensitization +                                   Br 1                        sulfur                                                                        sensitization                             20*      Cl 99 mol %                                                                          "    K.sub.4 [Fe(CN).sub.6 ]                                                              1 × 10.sup.-4                                                                   Gold    12600                                                                 sensitization +                                   Br 1                        sulfur                                                                        sensitization                            __________________________________________________________________________     *Invention                                                               

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A photographic silver halide emulsion comprisingsilver chorobromide grains containing at least 98.5 mol % silverchloride or silver chloride grains, wherein tabular grains having athickness of less than 0.5 μm, a diameter of at least 0.5 μm and anaspect ratio of at least 2/1 account for at least 50% of the totalprojected area of the silver halide grains, and said tabular grains areformed in the presence of a compound of a metal belonging to Group VIIIof the Periodic Table selected from the group consisting of iron,ruthenium and osmium.
 2. A photographic silver halide emulsion as inclaim 1, wherein the compound of a metal belonging to Group VIII of thePeriodic Table is present in an amount of from 1×10⁻⁸ to 1×10⁻² mol permol of silver halide contained in the emulsion.
 3. A photographic silverhalide emulsion as in claim 1, wherein the tabular grains have an aspectratio of from 3/1 to 8/1.
 4. A photographic silver halide emulsion as inclaim 1, wherein the tabular grains have a diameter of from 0.7 to 4 μm.5. A photographic silver halide emulsion as in claim 1, wherein thetabular grains have a thickness of less than 0.3 μm.
 6. A photographicsilver halide emulsion as in claim 1, wherein the tabular grains accountfor at least 70% of the total projected area of the silver halidegrains.
 7. A photographic silver halide emulsion as in claim 1, whereinthe silver chlorobromide grains contain at least 99% mol % silverchloride.
 8. A photographic silver halide emulsion as in claim 1,wherein said tabular grains comprise a localized silver bromide phasenear the surface of the grains.
 9. A light-sensitive silver halidephotographic material comprising a support having thereon at least onehydrophilic colloid layer, at least one layer of which is alight-sensitive silver halide emulsion layer comprising silverchlorobromide grains containing at least 98.5 mol % silver chloride orsilver chloride grains, wherein tabular grains having a thickness ofless than 0.5 μm, a diameter of at least 0.5 μm and an aspect ratio ofat least 2/1 account for at least 50% of the total projected area of thesilver halide grains, and said tabular grains are formed in the presenceof a compound of a metal belonging to Group VIII of the Periodic Tableselected from the group consisting of iron, ruthenium and osmium.